Comparative cradle-to-grave life cycle assessment of wood and alternative biomass pellet feedstocks for decentralized heating using experimental data

This study compares the cradle-to-grave environmental impacts of wood, alternative biomass, and wood and alternative biomass feedstock mixed pellets, using 1 MWh of thermal energy produced by pellet combustion as the functional unit. Experimental data underpin the assessment: proximate analyses, net calorific value, boiler efficiency, flue-gas emissions, and ash chemical composition. Impacts were evaluated with ReCiPe 2016 Endpoint (H/A). Brewer's spent grain (3.84 Pt) and sunflower husk (4.71 Pt) pellets show lower total impacts than wood pellets (6.87 Pt), while hemp has the highest (15.45 Pt). Observed patterns indicate that higher feedstock moisture is associated with increased collection and production impact, and nitrogen oxides concentration in flue gases is associated with higher combustion impact. Selected alternative feedstock can particularly reduce life-cycle impacts of specific processes relative to wood pellets for decentralized heating. The study provides region-specific primary evidence for pellet producers and biomass suppliers, boiler manufacturers seeking to optimize small-scale combustion of alternative pellets, and energy policymakers interested in promoting low-impact feedstocks in the local market and serves as a reference for future research in Latvia. • Alternative and mixed pellets reduce collection stage impact vs wood. • Brewer's spent grain pellets show lowest total impact per MWh thermal energy. • Wood and hemp mix pellets show the highest impact, mainly during combustion.